Electrical system



March 18, 1924. 1,486,890

R. E. HELLMUND ELECTRICAL SYSTEM Filed June` 18. 1919 2 Sheets-Sheet l aaa Jaa 40a t .fan 60o 70a /lAQl/CU@ me va/faye TTORNEY March 1s, 1924. 1,486,890

R; E. HELLMUND ELECTRICAL SYSTEM Filed June`vl8 1919 2 Sheets-Sheet 2 Joa A Line vo/aye v /aa son Jaa 4M A @MMF WITNEssEs: raund l INVENTOR )ff-JMW( Ruda/f E /ie//fm//la BY M ATTORNEY Patented Mar. 18, 1924.

RUDOLF E.

PATENT OFFICE.

HELLMUND, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORYTO` WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

ELECTRICAL SYSTEM.

Application led .Tune 18, 1919. Serial No. 305,106.

To all whom it may concern.'

Be it known that I, RUDOLF E. HELLMUND, a citizen of the German Empire, and a resident of Pittsburgh, in 'the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electrical Systems, of which the following is a specification.

My invention relates to electrical systems and particularly to train-lighting systems, or the like, where a substantially constant delivered voltage is desired.

One object of my inventionis to provide a system of the above-indicated character which shall be relatively quick-acting to compensate for the unavoidable fluctuations of trolley voltage, whereby a minimum degree of dicker of the car lamps occurs.

More specifically stated, it is the object of my invention to provide a motor-generator set, together with counter-voltage-producing means,such as an impedance, that is connected in circuit to receive certain combinations of the currents traversing the field windings of the motor-generator set, whereby thek desired result of producing a substantially constant voltage for the car lamps is secured.

Other objects of my invention will become evident from the following detailed description taken in conjunction with-the accompanying drawings, wherein Figure l is a diagrammatic view of any electrical system organized in accordance with the present invention;

Figs. 2, 6 and 8 to 11, inclusive, are diagrammatic views of modified forms of the invention, and

Figs. 3, 4, 5 and 7 are curve charts serving to indicatefvarious operating conditions of the illustrated systems.

Referring to Fig. 1 ofthe drawings, the system here shown comprises su ply-circuit conductors Trolley and Groun a motorgenerator set l; a resistor 2 or other countervoltage-producing means; a load circuit 3,

such as a plurality of car lamps; and a storage `battery 4 that is connected across the load for the purpose of further steadying the voltage applied thereto, in accordance with a familial` practice. l

The motor-ge'ninatorv set l comprises a motor armature winding A1. and a generator armature winding A2 that are mechanically associated, as by a shaft 5, together with a plurality of shunt field windings F1 and F2 and series field windings F3 and F4 for the respective armature windings A1 and A2.

The motor armature windin A1 is connected through the field windings F3 and F4 across the supply-circuit, while the generator armature winding A2 is directly connected to the set of lamps 3 and the storage battery 4. The field windings F2 and F1 are jointly connected between the lowervoltage terminals of the respective armature windings, and the resistor 2 is connected from a point intermediate the armature windings A1 and A2 to a point intermediate the shunt field windings F1 and F2.

The4 system shown in Fig. 2 omits the series field windings F3 and F4, but is otherwise identical with the system of Fig. l. The relative results of these two systems will be discussed below.

It is frequently the case that the voltage upon interurban cars is so variable, because ofthe severe voltage fluctuations or drops in the supply circuit, that satisfactory lighting effects cannot be obtained by connecting the lamps directly to the line. One method of obtaining a substantially constant voltage for the lamps is to install a motor-generator set including a shunt motor having an unsaturated fieldmagnetic circuit. Such a motor, if maintained unsaturated over the entire voltage range of the supply circuit and if having relatively low ohmic resistance, would possess approximately constant-speed characteristics, sothat a shunt-excited generator driven thereby wouldprovide a substantially constant voltage for the car lamps. However, a motor fulfilling the above conditions would be relatively large and expensive and is out of` the question for the majority of interurban lines. The present systems, therefore, have been devised to compensate for the above-mentioned fluctuations of supply-circuit voltage without requiring an unduly expensive motor-generator set.

Considering Fig. 2, for example, the resistor 2, vwhen connected as vdescribed above, carries the sum ofthe currents` traversing the motor field winding'F1andJthe generator field winding F2. Assuming tha els-the motor voltage,

@,:the generator voltage,

azthe resistance of the motor field Winding F l,

bzthe resist-ance of the generator field winding F2,

czthe resistance of the resistor 2,

zic-:the current in the motor field Winding F l, and

g/zthe current in the generator' eld Winding F2, the following equations (l) and (2) represent the values of the voltages c, and e2, expressed as functions of the currents a and g/ in the field windings:

Multiplynig out, equations (3) and (4) are obtained Equations (5) and (6) are obtained by regrouping,

6) @miniere f and equations (7) and (8) by multiplying equation (5) by the factor c and equation (6) by the binomial (tz-l-c).

te @geen:asociada-o tai-o Transposing and solving for y, equations (9) and (l0) are obtained In a similar manner, the value of :v as set forth 1n equation (ll) may be secured Consequently, by choosing proper values of the resistances e., Z) and c, it Will be seen that it is possible to cause the speed of the motor to decrease upon an increase of line voltage and to simultaneously augment the strength of the generator field Winding F2, so that the delivered voltage c2 of the generator armature remains substantially constant over a Wide range.

Fig. 3 shows the magnetic-saturation curve applying to the two machines, when connected as shown iii Fig. l or Fig. 2, the curve being plotted with field ainperes as abscissae and tlux values as ordinates.

Fig. elshows the voltage curve of the generator armature Winding or, in other Words, the lamp voltage is plotted against the line voltage. It Will be noted that the line voltage may 3e varied through a Working range from 380 to 700 volts, approximately, Without causing a generated voltage/variation of more than: from the average desired voltage for thelam s. The legends placed upon Fig. 4 Will o viate the necessity of any further explanation thereoft Considering Fig. l, which, as previously stated, adds the series lield windings F3 and Fi to the system of Fig. 2, whereby the liability to tlashover7 conditions in the motorgenerator set is greatly reduced, such a system will properly compensate for still greater variations of supply-circuit voltage, and should be employed Where the voltage regulation of the trolley circuit is still poorer than that assumed in connection With the system of Fig. 2 and the curve chart, Fig. 4.

The lamp voltage is again plotted against the line voltage in Fig. and it will be noted that a variation of not more than 4% from the average desired lighting voltage is provided by the generator arm ature A2 over a Working range from 280 to 650 volts, approximately.

It Will be appreciated, Without further illustration or description, that, if desired, the generator armature Winding A2 may be designed of su tticient capacity to provide the necessary excitation for the field windings of a main car-propelling motor during the regenerative period thereof, in addition to supplying the desired substantially constant voltage to the lighting circuits.

Referring to Fig. 6, the system shown comprises the mechanically-connected niotor-armature Winding Al and the generator`- armature Winding' A2, together with the field windings F2 and Fl, which are jointly connected between the loner-voltage terminal of the generator armature A2 and the higher-voltage terminal of the motor armature A l, and a resistor G which is connected in common series relation with the field windings Fl and F2. A series field Winding F3 is pro ided for the motor-armature Winding Al and may be short-circuited by a switch 7 to eliminate the ellect thereo't` whenever desired.

Instead of using a motor-generator set for furnishing the entire power to the load or lamp circuit, the connections of Fig. 6 may be employed, the switch 7 being considered as closed, whereby the supply-circuit voltage is impressed upon the nlotor-armature Winding Al. and the generator-armat ure winding A2 adds or snbtracls a certain voltage to or from the supply-circuit voltage to provide the desired electroinotive force vfor the lamps 3. In the present case, the motor ,field AWinding Fl is augmented in strength upon an increase of line voltage, whereinv the speed of the motor-generator set is reduced.

At the same time, the generator field Winding F2 decreases in strength and, consequently, the voltage of the generator armature A2 is materially7 reduced in such proportion that the sum of the voltages of the motor and the generator armatures is kept substantially constant. As stated above, one advantageof the )rese-nt arrangement over those previously described is that SFS ' 55 -4"The system just set y l tageover the previous figuresthat keacliiof` the energy that kis furnished by the motorgenerator setto the lampcircuit constitutes a relatively small percentage of the total energy required by the load. e vr It may be demonstrated mathematically,

ina manner similar to that set forth in 'connection with Fig. 2, that the lamp voltage may be maintained practically constant" over a relatively wide range of variationV of the /to insert the field winding F3 in circuit, it' lo will be observed that, since ay substantially constant lighting load is provided, the current taken' bythe motor-generator setifrom the supply circuit increases with Aa decrease in line voltage. Consequently,` the totalfield y flux. ott theinotor increases more rapidly upon a reductionof.supply-circuit voltage than'in the case when the series field winding.

FB-is inoperative, as fcon'ipared ,with the change' of `eld flux of thegenerator.` jAs i result, the opeiation'of the motorfgenerator set may bev rendered more sensitive, to*provide a moi-enearly constant delivered voltageto the lighting yfield winding F3 is utilized. Whenever the storage battery 4 is Hoated "across 'the load circuit, as illustrated, otherV systems of connections that are inherently not quite as satisfactory as those previously described may be employed, 'if reg'ulationby 40 the battery is depended upon to a material degree. Referring to Fig. `8, yfor example, -the system shown comprises the 'armature windings A1 and A2, which are' connectedl` in series relation with the field windings F3 and F4 across thev supply circuit, while the other field windings F1 and F2`areyjointly connected between the higher-voltage' terminals of the respective armature windings. The resistor 2 iskagain connected in common 5o series relation with the'field vwindings Fl and F2, and suitable switches "'and8 are provided for short-circuiting thefield windings F3 and F/lvto eliminatefth'e effect thereof whenever desired;`

forth :fthe4 advam the two machines may be made pf smaller current-carrying capacity byvr'easonK offthe`v`l purposes; if r`Insteadiof v9,"if`s desired, tlie'series field windings F3 and F4 may be excitedfby current from the series connection thereof'. Q'This arrangement co is'specially desirablefin theca'se of highvoltage systems', such as"1200fl volts," for invstance, since-thel use 1of "two 60G-volt machines connected in series relation'isy permit.-

e5, 'Assuming thattheiswitchesfi andare i ,with signe.

load, when the series,V

" The connection of the resistor rst closed to eliminate the effects of the series-fieldl windings F3 and Fliand that the .lincvoltage decreases, then the current in the generator field winding F2 and iii the resistor 2 willv correspondingly diminish. Upon alreducti'on in the current traversing the resistor2', while the voltage of the motor armature winding Al is maintained substantially y,coi/istant by reason of the illustrated relative connections of the `battery and the motorigenerator set, it follows that, since a smaller voltage drop occurs in the resistor 2, a larger voltage than normal will be impressed upon the motor field winding Fl to increase the current flow therethrough. Such increase yin `field current compensates partially or entirely forthe decreased speed of the motorgeneratorf set that is caused by the abovementioned drop in line voltage.

i lVhenever the switches 7 and 8 are opened, .the series ieldwindings F3 and F4 become activeto render the operation of the system more sensitive and toprovide closer voltage regiilation, as mentioned above in rconnection "Referringto Fig. 9, the system shown againq'comprises the armature windings Al and tA2, which are connected in seriesrelay'tion l'with the field windings F41 and F3 acrossthe Lsupply circuit, while the remaining field windings F1 and F2 are `iointly `connected between the lower-voltage terminals of thev respective armature windings.

,The'short-circuiting switches 7 and' 8 forthe K series-field windings F3 and F/i are'again' provided, while the resistor 2 is connected across a circuit including the motor-armature 'windingmAl and its field winding F1.

2 is such as'tocause it to carry the sum of the currents ktrwersing the two field windings F1 'and F2. Assuming that the line voltage drops,

the -cu'irentvin the resistor 2 and the voltage drop thereacross will likewise decrease. Consequently, a greater percentage of reduction of voltage occurs in the motor-field winding 'F1 than inthe generator-field winding F2.

In loth'er words, the strength of the field 'winding Fl is decreasedto a greater degree than thestrength of the field winding F2, which "action, therefore, tends to maintain the' i voltage Lof vthe `generator-armature winding A2. Y Such action maybe mathematically demonstrated at length, but it is not believed that such l`deinonstration is necessary here.' i-Iff-desiremthe switchesV 17' and 8 may bev opened to insert the series field windings F3 Y andfF; in :circuit for the above-mentioned the cnnectionsshown in Fig;

generatorurmature'A2 or by Vthe. load cur- 'irenti'f'traversingr the lamps 3. 'Furtherthe main car-propellino' motor is connected in seres relation with a stabilizing resistor 10. rlhe auxiliary generator armature A2 is con nected to ene 'ice lield winding F of the main machine rnrough the resistor l0, while the auxiliary motor armature il is connected through a field winding- F2 therefor and a variable resistor ll. across the supply circuit. il .field winding vfor the generator armature i12 1s connected, through the resistor 2, acr ss lthe resistor ll, and another resistor is connected, in series rc` lation with the resistor across the supply circuit.

rlfhe resistor traversing` as well as 2 thus carries the current the generator .field winding F3 the current iiowing` through the resistor 9. Consequently, i the line voltage drops, the current in the. resistors 9 and 2 correspondingly decreases. This action results in an increased voltage drop across the generator field winding F3 because ol" the connection thereot in parallel relation to the resistor il. whereby an increased field excitation tor the generator armature A2 is provided to rounterbale-.nce the decrease in supply-circuit voltage. ln this way, a dei sirably constant voltage is suppled by the generator armature i2 to thel field-winding circuit tor the main regenerating machine.

Referring to Fig. ll, similar results are obtained by connecting' the field windings lill and F8 for the auxiliary motor and auxil- 'ary generator*` respectively7 in parallel relation and in circuit with the resistor' One auxiliary circuit thus established through the motor arniature ill and the field winding' Fl toV groumh while a branch circuit is completed trom the lower-voltage terminal ot the motor armature Al through `he generator-field winding- F3 and the resist r 2 to ground. rlie rc2 i ors 9 and 2 are again connecten in series relation across the supply circuit.

ii Le YQ# Y Avv r aicn oi. the sg l do not wish to be restricted to the specific circuit connections or arrangement of I claim as my invention:

l. The combination with a motor armature winding and a generator armature winding driven thereby, of a plurality of lield windings tor exciting said armature windings, and counter-voltagev-producing means connected to receive certain combinations of the currents traversing said field windings.

ln an electrical system for the generation et a substantially constant voltage, the combination with a motor-generator set, of counter-voltage-producing means connected 'to receive certain combinations ot' exciting currents tor said motor-generator set- 3. ln an electrical system for the generaltion o'iE a substantially constant voltage7 the combination with a motor-generator set embodying a plurality of excitingy field windings, and a resistor connected in circuit wi li said field windings to receive a combination of the currents thereof.

de. The combination with a motor armature winding and a generator armature winding` driven thereby.y of a plurality of shunt Held windings for excitingT said armature windings. and a resistor' connected in circuit with said field windings to receive a combination of the currents thereof'.

o. The combination with a motor armature windingr and a generator armature winding driven thereby, ot a field winding` tor exciting the generator armature windinn. and counterfoliage-producing means connected in circuit with said field winding.;r to receive a combination ot the field-winding current and a current dependent upon the voltage ot said motor armature winding.

G. The combination with a motor armature winning and a generator armature windingr driven thereby, ot a` field winding for exciting the generator armature windine'. and counter-voltage-producing means connected in series relation with said field winding' to rece-ive the sum oit the field-winding current and a current dependent upon the impressed voltage ot said motor armature winding.

'i'. The combination with a supply circuit and a motor-generator set driven therefrom and comprisingT a field winding' tor the gcnerator. ot a resistor connected in series relation with said field winding to receive the sum @t the field-windimcY current and a current dependent upon the voltage of said supply circuit.

d. The combination with a motor armature windingT and a generator armature windingV driven thereby. of a plurality of field windings jointly connected across the lower-voltage terminals of the respective armature windings. counter-voltageproducin eir means connectingr a point intermediate the armature windings to a point intermediate the field windings, and a. plurality of other field windings for the respective armature windings connected in series rela.- tion with the motor armature winding.

9. The combination with a, motor arma.- 5 ture winding and a generator armature winding driven thereby, of a urality of field windings jointly connecte across the lower-voltage terminals of the respective armature windings, and a resistor connecting a point intermediate the armature windings to a point intermediate the field windings.

In testimony whereof, I have hereunto subscribed my name this 6th day of June RUDOLF E. HELLMUND. 

